Method of additive manufacturing by intermittent exposure

ABSTRACT

A method of forming a three-dimensional object, is carried out by: providing a carrier and an optically transparent member having a build surface, the carrier and the build surface defining a build region therebetween; filling the build region with a polymerizable liquid, intermittently irradiating the build region with light through the optically transparent member to form a solid polymer from the polymerizable liquid, and continuously or intermittently advancing the carrier away from the build surface to form the three-dimensional object from the solid polymer. In some embodiments, the filling, irradiating, and/or advancing steps are carried out while also concurrently: (i) continuously maintaining a dead zone of polymerizable liquid in contact with the build surface, and (ii) continuously maintaining a gradient of polymerization zone between the dead zone and the solid polymer and in contact with each thereof, the gradient of polymerization zone comprising the polymerizable liquid in partially cured form.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/545,148, filed Jul. 20, 2017, which is a 35 U.S.C. § 371 nationalphase entry of PCT Application PCT/US2016/016332, filed Feb. 3, 2016,and published in English on Aug. 11, 2016, as International PublicationNo. WO2016/126796, and which claims the benefit of U.S. ProvisionalPatent Application No. 62/112,290, filed Feb. 5, 2015, the disclosure ofeach of which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention concerns methods and apparatus for the fabricationof solid three-dimensional objects from liquid materials.

BACKGROUND OF THE INVENTION

In conventional additive or three-dimensional fabrication techniques,construction of a three-dimensional object is performed in a step-wiseor layer-by-layer manner. In particular, layer formation is performedthrough solidification of photo curable resin under the action ofvisible or UV light irradiation. Two techniques are known: one in whichnew layers are formed at the top surface of the growing object; theother in which new layers are formed at the bottom surface of thegrowing object.

If new layers are formed at the top surface of the growing object, thenafter each irradiation step the object under construction is loweredinto the resin “pool,” a new layer of resin is coated on top, and a newirradiation step takes place. An early example of such a technique isgiven in Hull, U.S. Pat. No. 5,236,637, at FIG. 3. A disadvantage ofsuch “top down” techniques is the need to submerge the growing object ina (potentially deep) pool of liquid resin and reconstitute a preciseoverlayer of liquid resin.

If new layers are formed at the bottom of the growing object, then aftereach irradiation step the object under construction must be separatedfrom the bottom plate in the fabrication well. An early example of sucha technique is given in Hull, U.S. Pat. No. 5,236,637, at FIG. 4. Whilesuch “bottom up” techniques hold the potential to eliminate the need fora deep well in which the object is submerged by instead lifting theobject out of a relatively shallow well or pool, a problem with such“bottom up” fabrication techniques, as commercially implemented, is thatextreme care must be taken, and additional mechanical elements employed,when separating the solidified layer from the bottom plate due tophysical and chemical interactions therebetween. For example, in U.S.Pat. No. 7,438,846, an elastic separation layer is used to achieve“non-destructive” separation of solidified material at the bottomconstruction plane. Other approaches, such as the B9Creator™3-dimensional printer marketed by B9Creations of Deadwood, S. Dak., USA,employ a sliding build plate. See, e.g., M. Joyce, U.S. Pat. App.2013/0292862 and Y. Chen et al., U.S. Pat. App. 2013/0295212 (both Nov.7, 2013); see also Y. Pan et al., J. Manufacturing Sci. and Eng. 134,051011-1 (October 2012). Such approaches introduce a mechanical stepthat may complicate the apparatus, slow the method, and/or potentiallydistort the end product.

Continuous processes for producing a three-dimensional object aresuggested at some length with respect to “top down” techniques in U.S.Pat. No. 7,892,474, but this reference does not explain how they may beimplemented in “bottom up” systems in a manner non-destructive to thearticle being produced. Accordingly, there is a need for alternatemethods and apparatus for three-dimensional fabrication that can obviatethe need for mechanical separation steps in “bottom-up” fabrication.

SUMMARY OF THE INVENTION

Described herein are methods, systems and apparatus (includingassociated control methods, systems and apparatus), for the productionof a three-dimensional object by additive manufacturing. In preferred(but not necessarily limiting) embodiments, the method is carried outcontinuously. In preferred (but not necessarily limiting) embodiments,the three-dimensional object is produced from a liquid interface. Hencethey are sometimes referred to, for convenience and not for purposes oflimitation, as “continuous liquid interphase printing” or “continuousliquid interface production” (“CLIP”) herein (the two being usedinterchangeably). See, e.g., J. Tumbleston et al., Continuous liquidinterface production of 3D objects, Science 347, 1349-1352 (publishedonline Mar. 16, 2015). A schematic representation is given in FIG. 1herein.

The present invention provides a method of forming a three-dimensionalobject, comprising:

providing a carrier and an optically transparent member having a buildsurface, said carrier and said build surface defining a build regiontherebetween;

filling said build region with a polymerizable liquid,

continuously or intermittently irradiating said build region with lightthrough said optically transparent member to form a solid polymer fromsaid polymerizable liquid, and

continuously or intermittently advancing (e.g., sequentially orconcurrently with said irradiating step) said carrier away from saidbuild surface to form said three-dimensional object from said solidpolymer.

In some embodiments, illumination is carried out sequentially, andpreferably at higher intensity (e.g., in “strobe” mode), as describedfurther below.

In some embodiments, fabrication is carried out in two or threesequential patterns, from a base zone, through an optional transitionzone, to a body zone, as described further below.

In some embodiments, the carrier is vertically reciprocated with respectto the build surface to enhance or speed the refilling of the buildregion with the polymerizable liquid.

Preferably the filling, irradiating, and/or advancing steps are carriedout while also concurrently: (i) continuously maintaining a dead zone ofpolymerizable liquid in contact with said build surface, and (ii)continuously maintaining a gradient of polymerization zone between saiddead zone and said solid polymer and in contact with each thereof, saidgradient of polymerization zone comprising said polymerizable liquid inpartially cured form. The dead zone and gradient of polymerization zonemay be maintained through some or all of the formation of the objectbeing made, for example (and in some embodiments) for a time of at least5, 10, 20, or 30 seconds, and in some embodiments for a time of at least1 or 2 minutes.

Apparatus for carrying out the present invention generally comprises:

(a) a support;

(b) a carrier operatively associated with said support on which carriersaid three-dimensional object is formed;

(c) an optically transparent member having a build surface, with saidbuild surface and said carrier defining a build region therebetween;

(d) a liquid polymer supply operatively associated with said buildsurface and configured to supply liquid polymer into said build regionfor solidification or polymerization;

(e) a radiation source configured to irradiate said build region throughsaid optically transparent member to form a solid polymer from saidpolymerizable liquid;

(f) optionally at least one drive operatively associated with eithersaid transparent member or said carrier;

(g) a controller operatively associated with said carrier, and/oroptionally said at least one drive, and said radiation source foradvancing said carrier away from said build surface to form saidthree-dimensional object from said solid polymer,

with the controller preferably further configured to oscillate orreciprocate said carrier with respect to said build surface to enhanceor speed the refilling of said build region with said polymerizableliquid.

In some embodiments, the polymerizable liquid comprises a mixture of (i)a light polymerizable liquid first component, and (ii) a secondsolidifiable component that is different from the first component. Inthis case, th method may further include, concurrently with or followingthe forming of the three dimensional object, solidifying and/or curingthe second solidifiable component in the three-dimensional object (e.g.,by removing the three-dimensional object as an “intermediate” objectfrom the carrier, and heating and/or microwave irradiating the object).

In some embodiments, the second component comprises a polymerizableliquid solubilized in or suspended in the first component.

In some embodiments, the second component comprises: (i) a polymerizablesolid suspended in the first component; (ii) a polymerizable solidsolubilized in the first component; or (iii) a polymer solubilized inthe first component.

In some embodiments, the three-dimensional intermediate is collapsibleor compressible.

In some embodiments, the three-dimensional object, following the furthersolidifying and/or curing, comprises a polymer blend, interpenetratingpolymer network, semi-interpenetrating polymer network, or sequentialinterpenetrating polymer network formed from the first component and thesecond component.

In some embodiments, the polymerizable liquid comprises: from 1 or 10percent by weight to 40, 90 or 99 percent by weight of the firstcomponent; and from 1, 10 or 60 percent by weight to 90 or 99 percent byweight of the second component.

In some embodiments, the further solidifying and/or curing step (d) iscarried out concurrently with the irradiating step (c) and: (i) thesolidifying and/or curing step is carried out by precipitation; or (ii)the irradiating step generates heat from the polymerization of the firstcomponent in an amount sufficient to thermally solidify or polymerizethe second component.

In some embodiments, the further solidifying and/or curing step iscarried out subsequent to the irradiating step (c) and is carried outby: (i) heating the second solidifiable component; (ii) irradiating thesecond solidifiable component with light at a wavelength different fromthat of the light in the irradiating step (c); (iii) contacting thesecond polymerizable component to water; and/or (iv) contacting thesecond polymerizable component to a catalyst.

In some embodiments, the second component comprises the precursors to apolyurethane, polyurea, or copolymer thereof, a silicone resin, an epoxyresin, a cyanate ester resin, or a natural rubber; and the solidifyingstep is carried out by heating and/or microwave irradiating.

In some embodiments, the second component comprises the precursors to apolyurethane, polyurea, or copolymer thereof, and the solidifying and/orcuring step is carried out by contacting the second component to water.

In some embodiments, the further solidifying and/or curing step iscarried out subsequent to the irradiating step; and the solidifyingand/or curing step is carried out under conditions in which the solidpolymer scaffold degrades and forms a constituent necessary for thepolymerization of the second component.

In some embodiments, the second component comprises precursors to apolyurethane, polyurea, or copolymer thereof, a silicone resin, aring-opening metathesis polymerization resin, or a click chemistryresin, a cyanate ester resin, and the solidifying and/or curing step iscarried out by contacting the second component to a polymerizationcatalyst.

In some embodiments, the polymerizable liquid comprises a firstcomponent (Part A) and at least one additional component (Part B), thefirst component comprising monomers and/or prepolymers that can bepolymerized by exposure to actinic radiation or light; the secondcomponent solidifiable on contacting to heat, water, water vapor, lightat a different wavelength than that at which the first component ispolymerized, catalysts, evaporation of a solvent from the polymerizableliquid, exposure to microwave irradiation, and combinations thereof.

In some embodiments employing two-component polymerizable liquids, thethree-dimensional object comprises an interpenetrating polymer network(IPN), the interpenetrating polymer network comprising a sol-gelcomposition, a hydrophobic-hydrophilic IPN, a phenolic resin, apolyimide, a conductive polymer, a natural product-based IPN, asequential IPN, a polyolefin, or a combination thereof.

Non-limiting examples and specific embodiments of the present inventionare explained in greater detail in the drawings herein and thespecification set forth below. The disclosure of all United StatesPatent references cited herein are to be incorporated herein byreference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of a method of thepresent invention.

FIG. 2 is a perspective view of one embodiment of an apparatus of thepresent invention.

FIG. 3 is a first flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 4 is a second flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 5 is a third flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 6 is a graphic illustration of a process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out continuously. Advancing of the carrier isillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 7 is a graphic illustration of another process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out stepwise, yet the dead zone and gradient ofpolymerization are maintained. Advancing of the carrier is againillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 8 is a graphic illustration of still another process of theinvention indicating the position of the carrier in relation to thebuild surface or plate, where both advancing of the carrier andirradiation of the build region is carried out stepwise, the dead zoneand gradient of polymerization are maintained, and a reciprocating stepis introduced between irradiation steps to enhance the flow ofpolymerizable liquid into the build region. Advancing of the carrier isagain illustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 9 is a detailed illustration of a reciprocation step of FIG. 23,showing a period of acceleration occurring during the upstroke (i.e., agradual start of the upstroke) and a period of deceleration occurringduring the downstroke (i.e., a gradual end to the downstroke).

FIG. 10 schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byprocesses of the present invention through a first base (or “adhesion”)zone, a second transition zone, and a third body zone.

FIG. 11A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object bycontinuous advancing and continuous exposure.

FIG. 11B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 11A, except that illumination is now in anintermittent (or “strobe”) pattern.

FIG. 12A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byintermittent (or “stepped”) advancing and intermittent exposure.

FIG. 12B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 12A, except that illumination is now in ashortened intermittent (or “strobe”) pattern.

FIG. 13A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byoscillatory advancing and intermittent exposure.

FIG. 13B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 13A, except that illumination is now in ashortened intermittent (or “strobe”) pattern.

FIG. 14A schematically illustrates one segment of a “strobe” pattern offabrication, where the duration of the static portion of the carrier hasbeen shortened to near the duration of the “strobe” exposure

FIG. 14B is a schematic illustration of a segment of a strobe pattern offabrication similar to FIG. 14A, except that the carrier is now movingslowly upward during the period of strobe illumination.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Where used, broken lines illustrate optionalfeatures or operations unless specified otherwise.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements components and/orgroups or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups or combinations thereof.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on,”“attached” to, “connected” to, “coupled” with, “contacting,” etc.,another element, it can be directly on, attached to, connected to,coupled with and/or contacting the other element or intervening elementscan also be present. In contrast, when an element is referred to asbeing, for example, “directly on,” “directly attached” to, “directlyconnected” to, “directly coupled” with or “directly contacting” anotherelement, there are no intervening elements present. It will also beappreciated by those of skill in the art that references to a structureor feature that is disposed “adjacent” another feature can have portionsthat overlap or underlie the adjacent feature.

Spatially relative terms, such as “under,” “below,” “lower,” “over,”“upper” and the like, may be used herein for ease of description todescribe an element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus the exemplary term “under” can encompass both anorientation of over and under. The device may otherwise be oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly,” “downwardly,” “vertical,” “horizontal” and the like are usedherein for the purpose of explanation only, unless specificallyindicated otherwise.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. Rather, these terms areonly used to distinguish one element, component, region, layer and/orsection, from another element, component, region, layer and/or section.Thus, a first element, component, region, layer or section discussedherein could be termed a second element, component, region, layer orsection without departing from the teachings of the present invention.The sequence of operations (or steps) is not limited to the orderpresented in the claims or figures unless specifically indicatedotherwise.

1. Polymerizable Liquids/Part A Components

Any suitable polymerizable liquid can be used to enable the presentinvention. In some embodiments, the polymerizable liquid comprises, inaddition to a first component (or “part A”) such as described in thissection, a second component (or “part B”) such as described in the “DualHardening” section below. The liquid (sometimes also referred to as“liquid resin” “ink,” or simply “resin” herein) can include a monomer,particularly photopolymerizable and/or free radical polymerizablemonomers, and a suitable initiator such as a free radical initiator, andcombinations thereof. Examples include, but are not limited to,acrylics, methacrylics, acrylamides, styrenics, olefins, halogenatedolefins, cyclic alkenes, maleic anhydride, alkenes, alkynes, carbonmonoxide, functionalized oligomers, multifunctional cute site monomers,functionalized PEGs, etc., including combinations thereof. Examples ofliquid resins, monomers and initiators include but are not limited tothose set forth in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476;7,767,728; 7,649,029; WO 2012129968 A1; CN 102715751 A; JP 2012210408 A.

Acid catalyzed polymerizable liquids. While in some embodiments as notedabove the polymerizable liquid comprises a free radical polymerizableliquid (in which case an inhibitor may be oxygen as described below), inother embodiments the polymerizable liquid comprises an acid catalyzed,or cationically polymerized, polymerizable liquid. In such embodimentsthe polymerizable liquid comprises monomers contain groups suitable foracid catalysis, such as epoxide groups, vinyl ether groups, etc. Thussuitable monomers include olefins such as methoxyethene,4-methoxystyrene, styrene, 2-methylprop-1-ene, 1,3-butadiene, etc.;heterocycloic monomers (including lactones, lactams, and cyclic amines)such as oxirane, thietane, tetrahydrofuran, oxazoline, 1,3, dioxepane,oxetan-2-one, etc., and combinations thereof. A suitable (generallyionic or non-ionic) photoacid generator (PAG) is included in the acidcatalyzed polymerizable liquid, examples of which include, but are notlimited to onium salts, sulfonium and iodonium salts, etc., such asdiphenyl iodide hexafluorophosphate, diphenyl iodide hexafluoroarsenate,diphenyl iodide hexafluoroantimonate, diphenyl p-methoxyphenyl triflate,diphenyl p-toluenyl triflate, diphenyl p-isobutylphenyl triflate,diphenyl p-tert-butylphenyl triflate, triphenylsulfoniumhexafluororphosphate, triphenylsulfonium hexafluoroarsenate,triphenylsulfonium hexafluoroantimonate, triphenylsulfonium triflate,dibutylnaphthylsulfonium triflate, etc., including mixtures thereof.See, e.g., U.S. Pat. Nos. 7,824,839; 7,550,246; 7,534,844; 6,692,891;5,374,500; and 5,017,461; see also Photoacid Generator Selection Guidefor the electronics industry and energy curable coatings (BASF 2010).

Hydrogels. In some embodiments suitable resins includes photocurablehydrogels like poly(ethylene glycols) (PEG) and gelatins. PEG hydrogelshave been used to deliver a variety of biologicals, including Growthfactors; however, a great challenge facing PEG hydrogels crosslinked bychain growth polymerizations is the potential for irreversible proteindamage. Conditions to maximize release of the biologicals fromphotopolymerized PEG diacrylate hydrogels can be enhanced by inclusionof affinity binding peptide sequences in the monomer resin solutions,prior to photopolymerization allowing sustained delivery. Gelatin is abiopolymer frequently used in food, cosmetic, pharmaceutical andphotographic industries. It is obtained by thermal denaturation orchemical and physical degradation of collagen. There are three kinds ofgelatin, including those found in animals, fish and humans. Gelatin fromthe skin of cold water fish is considered safe to use in pharmaceuticalapplications. UV or visible light can be used to crosslink appropriatelymodified gelatin. Methods for crosslinking gelatin include curederivatives from dyes such as Rose Bengal.

Photocurable silicone resins. A suitable resin includes photocurablesilicones. UV cure silicone rubber, such as Siliopren™ UV Cure SiliconeRubber can be used as can LOCTITE™ Cure Silicone adhesives sealants.Applications include optical instruments, medical and surgicalequipment, exterior lighting and enclosures, electricalconnectors/sensors, fiber optics and gaskets.

Biodegradable resins. Biodegradable resins are particularly importantfor implantable devices to deliver drugs or for temporary performanceapplications, like biodegradable screws and stents (U.S. Pat. Nos.7,919,162; 6,932,930). Biodegradable copolymers of lactic acid andglycolic acid (PLGA) can be dissolved in PEG dimethacrylate to yield atransparent resin suitable for use. Polycaprolactone and PLGA oligomerscan be functionalized with acrylic or methacrylic groups to allow themto be effective resins for use.

Photocurable polyurethanes. A particularly useful resin is photocurablepolyurethanes. A photopolymerizable polyurethane composition comprising(1) a polyurethane based on an aliphatic diisocyanate,poly(hexamethylene isophthalate glycol) and, optionally, 1,4-butanediol;(2) a polyfunctional acrylic ester; (3) a photoinitiator; and (4) ananti-oxidant, can be formulated so that it provides a hard,abrasion-resistant, and stain-resistant material (U.S. Pat. No.4,337,130). Photocurable thermoplastic polyurethane elastomersincorporate photoreactive diacetylene diols as chain extenders.

High performance resins. In some embodiments, high performance resinsare used. Such high performance resins may sometimes require the use ofheating to melt and/or reduce the viscosity thereof, as noted above anddiscussed further below. Examples of such resins include, but are notlimited to, resins for those materials sometimes referred to as liquidcrystalline polymers of esters, ester-imide, and ester-amide oligomers,as described in U.S. Pat. Nos. 7,507,784; 6,939,940. Since such resinsare sometimes employed as high-temperature thermoset resins, in thepresent invention they further comprise a suitable photoinitiator suchas benzophenone, anthraquinone, and fluoroenone initiators (includingderivatives thereof), to initiate cross-linking on irradiation, asdiscussed further below.

Additional example resins. Particularly useful resins for dentalapplications include EnvisionTEC's Clear Guide, EnvisionTEC's E-DenstoneMaterial. Particularly useful resins for hearing aid industries includeEnvisionTEC's e-Shell 300 Series of resins. Particularly useful resinsinclude EnvisionTEC's HTM140IV High Temperature Mold Material for usedirectly with vulcanized rubber in molding/casting applications. Aparticularly useful material for making tough and stiff parts includesEnvisionTEC's RC31 resin. A particularly useful resin for investmentcasting applications includes EnvisionTEC's Easy Cast EC500.

Additional resin ingredients. The liquid resin or polymerizable materialcan have solid particles suspended or dispersed therein. Any suitablesolid particle can be used, depending upon the end product beingfabricated. The particles can be metallic, organic/polymeric, inorganic,or composites or mixtures thereof. The particles can be nonconductive,semi-conductive, or conductive (including metallic and non-metallic orpolymer conductors); and the particles can be magnetic, ferromagnetic,paramagnetic, or nonmagnetic. The particles can be of any suitableshape, including spherical, elliptical, cylindrical, etc. The particlescan comprise an active agent or detectable compound as described below,though these may also be provided dissolved solubilized in the liquidresin as also discussed below. For example, magnetic or paramagneticparticles or nanoparticles can be employed. The resin or polymerizablematerial may contain a dispersing agent, such as an ionic surfactant, anon-ionic surfactant, a block copolymer, or the like.

The liquid resin can have additional ingredients solubilized therein,including pigments, dyes, active compounds or pharmaceutical compounds,detectable compounds (e.g., fluorescent, phosphorescent, radioactive),etc., again depending upon the particular purpose of the product beingfabricated. Examples of such additional ingredients include, but are notlimited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA,sugars, small organic compounds (drugs and drug-like compounds), etc.,including combinations thereof.

Inhibitors of polymerization. Inhibitors or polymerization inhibitorsfor use in the present invention may be in the form of a liquid or agas. In some embodiments, gas inhibitors are preferred. The specificinhibitor will depend upon the monomer being polymerized and thepolymerization reaction. For free radical polymerization monomers, theinhibitor can conveniently be oxygen, which can be provided in the formof a gas such as air, a gas enriched in oxygen (optionally but in someembodiments preferably containing additional inert gases to reducecombustibility thereof), or in some embodiments pure oxygen gas. Inalternate embodiments, such as where the monomer is polymerized byphotoacid generator initiator, the inhibitor can be a base such asammonia, trace amines (e.g. methyl amine, ethyl amine, di and trialkylamines such as dimethyl amine, diethyl amine, trimethyl amine, triethylamine, etc.), or carbon dioxide, including mixtures or combinationsthereof.

Polymerizable liquids carrying live cells. In some embodiments, thepolymerizable liquid may carry live cells as “particles” therein. Suchpolymerizable liquids are generally aqueous, and may be oxygenated, andmay be considered as “emulsions” where the live cells are the discretephase. Suitable live cells may be plant cells (e.g., monocot, dicot),animal cells (e.g., mammalian, avian, amphibian, reptile cells),microbial cells (e.g., prokaryote, eukaryote, protozoal, etc.), etc. Thecells may be of differentiated cells from or corresponding to any typeof tissue (e.g., blood, cartilage, bone, muscle, endocrine gland,exocrine gland, epithelial, endothelial, etc.), or may beundifferentiated cells such as stem cells or progenitor cells. In suchembodiments the polymerizable liquid can be one that forms a hydrogel,including but not limited to those described in U.S. Pat. Nos.7,651,683; 7,651,682; 7,556,490; 6,602,975; 5,836,313; etc.

2. Apparatus

A non-limiting embodiment of an apparatus of the invention is shown inFIG. 2. It comprises a radiation source 11 such as a digital lightprocessor (DLP) providing electromagnetic radiation 12 which thoughreflective mirror 13 illuminates a build chamber defined by wall 14 anda rigid build plate 15 forming the bottom of the build chamber, whichbuild chamber is filled with liquid resin 16. The bottom of the chamber15 is constructed of rigid build plate comprising a rigid semipermeablemember as discussed further below. The top of the object underconstruction 17 is attached to a carrier 18. The carrier is driven inthe vertical direction by linear stage 19, although alternate structurescan be used as discussed below.

A liquid resin reservoir, tubing, pumps liquid level sensors and/orvalves can be included to replenish the pool of liquid resin in thebuild chamber (not shown for clarity) though in some embodiments asimple gravity feed may be employed. Drives/actuators for the carrier orlinear stage, along with associated wiring, can be included inaccordance with known techniques (again not shown for clarity). Thedrives/actuators, radiation source, and in some embodiments pumps andliquid level sensors can all be operatively associated with a suitablecontroller, again in accordance with known techniques.

Build plates 15 used to carry out the present invention generallycomprise or consist of a (typically rigid or solid, stationary, and/orfixed) semipermeable (or gas permeable) member, alone or in combinationwith one or more additional supporting substrates (e.g., clamps andtensioning members to rigidify an otherwise flexible semipermeablematerial). The rigid semipermeable member can be made of any suitablematerial that is optically transparent at the relevant wavelengths (orotherwise transparent to the radiation source, whether or not it isvisually transparent as perceived by the human eye—i.e., an opticallytransparent window may in some embodiments be visually opaque),including but not limited to porous or microporous glass, and the rigidgas permeable polymers used for the manufacture of rigid gas permeablecontact lenses. See, e.g., Norman G. Gaylord, U.S. Pat. No. RE31,406;see also U.S. Pat. Nos. 7,862,176; 7,344,731; 7,097,302; 5,349,394;5,310,571; 5,162,469; 5,141,665; 5,070,170; 4,923,906; and 4,845,089. Insome embodiments such materials are characterized as glassy and/oramorphous polymers and/or substantially crosslinked that they areessentially non-swellable. Preferably the rigid semipermeable member isformed of a material that does not swell when contacted to the liquidresin or material to be polymerized (i.e., is “non-swellable”). Suitablematerials for the rigid semipermeable member include rigid amorphousfluoropolymers, such as those described in U.S. Pat. Nos. 5,308,685 and5,051,115. For example, such fluoropolymers are particularly useful oversilicones that would potentially swell when used in conjunction withorganic liquid resin inks to be polymerized. For some liquid resin inks,such as more aqueous-based monomeric systems and/or some polymeric resinink systems that have low swelling tendencies, silicone based windowmaterials maybe suitable. The solubility or permeability of organicliquid resin inks can be dramatically decreased by a number of knownparameters including increasing the crosslink density of the windowmaterial or increasing the molecular weight of the liquid resin ink. Insome embodiments the build plate may be formed from a thin film or sheetof material which is flexible when separated from the apparatus of theinvention, but which is clamped and tensioned when installed in theapparatus (e.g., with a tensioning ring) so that it is rendered rigid inthe apparatus. Particular materials include TEFLON AF® fluoropolymers,commercially available from DuPont. Additional materials includeperfluoropolyether polymers such as described in U.S. Pat. Nos.8,268,446; 8,263,129; 8,158,728; and 7,435,495.

It will be appreciated that essentially all solid materials, and most ofthose described above, have some inherent “flex” even though they may beconsidered “rigid,” depending on factors such as the shape and thicknessthereof and environmental factors such as the pressure and temperatureto which they are subjected. In addition, the terms “stationary” or“fixed” with respect to the build plate is intended to mean that nomechanical interruption of the process occurs, or no mechanism orstructure for mechanical interruption of the process (as in alayer-by-layer method or apparatus) is provided, even if a mechanism forincremental adjustment of the build plate (for example, adjustment thatdoes not lead to or cause collapse of the gradient of polymerizationzone) is provided).

The semipermeable member typically comprises a top surface portion, abottom surface portion, and an edge surface portion. The build surfaceis on the top surface portion; and the feed surface may be on one, two,or all three of the top surface portion, the bottom surface portion,and/or the edge surface portion. In the embodiment illustrated in FIG. 2the feed surface is on the bottom surface portion, but alternateconfigurations where the feed surface is provided on an edge, and/or onthe top surface portion (close to but separate or spaced away from thebuild surface) can be implemented with routine skill.

The semipermeable member has, in some embodiments, a thickness of from0.01, 0.1 or 1 millimeters to 10 or 100 millimeters, or more (dependingupon the size of the item being fabricated, whether or not it islaminated to or in contact with an additional supporting plate such asglass, etc., as discussed further below.

The permeability of the semipermeable member to the polymerizationinhibitor will depend upon conditions such as the pressure of theatmosphere and/or inhibitor, the choice of inhibitor, the rate or speedof fabrication, etc. In general, when the inhibitor is oxygen, thepermeability of the semipermeable member to oxygen may be from 10 or 20Barrers, up to 1000 or 2000 Barrers, or more. For example, asemipermeable member with a permeability of 10 Barrers used with a pureoxygen, or highly enriched oxygen, atmosphere under a pressure of 150PSI may perform substantially the same as a semipermeable member with apermeability of 500 Barrers when the oxygen is supplied from the ambientatmosphere under atmospheric conditions.

Thus, the semipermeable member may comprise a flexible polymer film(having any suitable thickness, e.g., from 0.001, 0.01, 0.05, 0.1 or 1millimeters to 1, 5, 10, or 100 millimeters, or more), and the buildplate may further comprise a tensioning member (e.g., a peripheral clampand an operatively associated strain member or stretching member, as ina “drum head”; a plurality of peripheral clamps, etc., includingcombinations thereof) connected to the polymer film and to fix andrigidify the film (e.g., at least sufficiently so that the film does notstick to the object as the object is advanced and resiliently orelastically rebound therefrom). The film has a top surface and a bottomsurface, with the build surface on the top surface and the feed surfacepreferably on the bottom surface. In other embodiments, thesemipermeable member comprises: (i) a polymer film layer (having anysuitable thickness, e.g., from 0.001, 0.01, 0.1 or 1 millimeters to 5,10 or 100 millimeters, or more), having a top surface positioned forcontacting said polymerizable liquid and a bottom surface, and (ii) arigid, gas permeable, optically transparent supporting member (havingany suitable thickness, e.g., from 0.01, 0.1 or 1 millimeters to 10,100, or 200 millimeters, or more), contacting said film layer bottomsurface. The supporting member has a top surface contacting the filmlayer bottom surface, and the supporting member has a bottom surfacewhich may serve as the feed surface for the polymerization inhibitor.Any suitable materials that are semipermeable (that is, permeable to thepolymerization inhibitor) may be used. For example, the polymer film orpolymer film layer may, for example, be a fluoropolymer film, such as anamorphous thermoplastic fluoropolymer like TEFLON AF 1600™ or TEFLON AF2400™ fluoropolymer films, or perfluoropolyether (PFPE), particularly acrosslinked PFPE film, or a crosslinked silicone polymer film. Thesupporting member comprises a silicone or crosslinked silicone polymermember such as a polydmiethylxiloxane member, a rigid gas permeablepolymer member, or a porous or microporous glass member. Films can belaminated or clamped directly to the rigid supporting member withoutadhesive (e.g., using PFPE and PDMS materials), or silane couplingagents that react with the upper surface of a PDMS layer can be utilizedto adhere to the first polymer film layer. UV-curable,acrylate-functional silicones can also be used as a tie layer betweenUV-curable PFPEs and rigid PDMS supporting layers.

When configured for placement in the apparatus, the carrier defines a“build region” on the build surface, within the total area of the buildsurface. Because lateral “throw” (e.g., in the X and/or Y directions) isnot required in the present invention to break adhesion betweensuccessive layers, as in the Joyce and Chen devices noted previously,the area of the build region within the build surface may be maximized(or conversely, the area of the build surface not devoted to the buildregion may be minimized). Hence in some embodiments, the total surfacearea of the build region can occupy at least fifty, sixty, seventy,eighty, or ninety percent of the total surface area of the buildsurface.

As shown in FIG. 2, the various components are mounted on a support orframe assembly 20. While the particular design of the support or frameassembly is not critical and can assume numerous configurations, in theillustrated embodiment it is comprised of a base 21 to which theradiation source 11 is securely or rigidly attached, a vertical member22 to which the linear stage is operatively associated, and a horizontaltable 23 to which wall 14 is removably or securely attached (or on whichthe wall is placed), and with the build plate rigidly fixed, eitherpermanently or removably, to form the build chamber as described above.

As noted above, the build plate can consist of a single unitary andintegral piece of a rigid semipermeable member, or can compriseadditional materials. For example, a porous or microporous glass can belaminated or fixed to a rigid semipermeable material. Or, asemipermeable member as an upper portion can be fixed to a transparentlower member having purging channels formed therein for feeding gascarrying the polymerization inhibitor to the semipermeable member(through which it passes to the build surface to facilitate theformation of a release layer of unpolymerized liquid material, as notedabove and below). Such purge channels may extend fully or partiallythrough the base plate: For example, the purge channels may extendpartially into the base plate, but then end in the region directlyunderlying the build surface to avoid introduction of distortion.Specific geometries will depend upon whether the feed surface for theinhibitor into the semipermeable member is located on the same side oropposite side as the build surface, on an edge portion thereof, or acombination of several thereof.

Any suitable radiation source (or combination of sources) can be used,depending upon the particular resin employed, including electron beamand ionizing radiation sources. In a preferred embodiment the radiationsource is an actinic radiation source, such as one or more lightsources, and in particular one or more ultraviolet light sources. Anysuitable light source can be used, such as incandescent lights,fluorescent lights, phosphorescent or luminescent lights, a laser,light-emitting diode, etc., including arrays thereof. The light sourcepreferably includes a pattern-forming element operatively associatedwith a controller, as noted above. In some embodiments, the light sourceor pattern forming element comprises a digital (or deformable)micromirror device (DMD) with digital light processing (DLP), a spatialmodulator (SLM), or a microelectromechanical system (MEMS) mirror array,a mask (aka a reticle), a silhouette, or a combination thereof. See,U.S. Pat. No. 7,902,526. Preferably the light source comprises a spatiallight modulation array such as a liquid crystal light valve array ormicromirror array or DMD (e.g., with an operatively associated digitallight processor, typically in turn under the control of a suitablecontroller), configured to carry out exposure or irradiation of thepolymerizable liquid without a mask, e.g., by maskless photolithography.See, e.g., U.S. Pat. Nos. 6,312,134; 6,248,509; 6,238,852; and5,691,541.

In some embodiments, as discussed further below, there may be movementin the X and/or Y directions concurrently with movement in the Zdirection, with the movement in the X and/or Y direction hence occurringduring polymerization of the polymerizable liquid (this is in contrastto the movement described in Y. Chen et al., or M. Joyce, supra, whichis movement between prior and subsequent polymerization steps for thepurpose of replenishing polymerizable liquid). In the present inventionsuch movement may be carried out for purposes such as reducing “burn in”or fouling in a particular zone of the build surface.

Because an advantage of some embodiments of the present invention isthat the size of the build surface on the semipermeable member (i.e.,the build plate or window) may be reduced due to the absence of arequirement for extensive lateral “throw” as in the Joyce or Chendevices noted above, in the methods, systems and apparatus of thepresent invention lateral movement (including movement in the X and/or Ydirection or combination thereof) of the carrier and object (if suchlateral movement is present) is preferably not more than, or less than,80, 70, 60, 50, 40, 30, 20, or even 10 percent of the width (in thedirection of that lateral movement) of the build region.

While in some embodiments the carrier is mounted on an elevator toadvance up and away from a stationary build plate, on other embodimentsthe converse arrangement may be used: That is, the carrier may be fixedand the build plate lowered to thereby advance the carrier awaytherefrom. Numerous different mechanical configurations will be apparentto those skilled in the art to achieve the same result.

Depending on the choice of material from which the carrier isfabricated, and the choice of polymer or resin from which the article ismade, adhesion of the article to the carrier may sometimes beinsufficient to retain the article on the carrier through to completionof the finished article or “build.” For example, an aluminum carrier mayhave lower adhesion than a poly(vinyl chloride) (or “PVC”) carrier.Hence one solution is to employ a carrier comprising a PVC on thesurface to which the article being fabricated is polymerized. If thispromotes too great an adhesion to conveniently separate the finishedpart from the carrier, then any of a variety of techniques can be usedto further secure the article to a less adhesive carrier, including butnot limited to the application of adhesive tape such as “Greener MaskingTape for Basic Painting #2025 High adhesion” to further secure thearticle to the carrier during fabrication.

3. Controller and Process Control

The methods and apparatus of the invention can include process steps andapparatus features to implement process control, including feedback andfeed-forward control, to, for example, enhance the speed and/orreliability of the method.

A controller for use in carrying out the present invention may beimplemented as hardware circuitry, software, or a combination thereof.In one embodiment, the controller is a general purpose computer thatruns software, operatively associated with monitors, drives, pumps, andother components through suitable interface hardware and/or software.Suitable software for the control of a three-dimensional printing orfabrication method and apparatus as described herein includes, but isnot limited to, the ReplicatorG open source 3d printing program,3DPrint™ controller software from 3D systems, Slic3r, Skeinforge,KISSlicer, Repetier-Host, PrintRun, Cura, etc., including combinationsthereof.

Process parameters to directly or indirectly monitor, continuously orintermittently, during the process (e.g., during one, some or all ofsaid filling, irradiating and advancing steps) include, but are notlimited to, irradiation intensity, temperature of carrier, polymerizableliquid in the build zone, temperature of growing product, temperature ofbuild plate, pressure, speed of advance, pressure, force (e.g., exertedon the build plate through the carrier and product being fabricated),strain (e.g., exerted on the carrier by the growing product beingfabricated), thickness of release layer, etc.

Known parameters that may be used in feedback and/or feed-forwardcontrol systems include, but are not limited to, expected consumption ofpolymerizable liquid (e.g., from the known geometry or volume of thearticle being fabricated), degradation temperature of the polymer beingformed from the polymerizable liquid, etc.

Process conditions to directly or indirectly control, continuously orstep-wise, in response to a monitored parameter, and/or known parameters(e.g., during any or all of the process steps noted above), include, butare not limited to, rate of supply of polymerizable liquid, temperature,pressure, rate or speed of advance of carrier, intensity of irradiation,duration of irradiation (e.g. for each “slice”), etc.

For example, the temperature of the polymerizable liquid in the buildzone, or the temperature of the build plate, can be monitored, directlyor indirectly with an appropriate thermocouple, non-contact temperaturesensor (e.g., an infrared temperature sensor), or other suitabletemperature sensor, to determine whether the temperature exceeds thedegradation temperature of the polymerized product. If so, a processparameter may be adjusted through a controller to reduce the temperaturein the build zone and/or of the build plate. Suitable process parametersfor such adjustment may include: decreasing temperature with a cooler,decreasing the rate of advance of the carrier, decreasing intensity ofthe irradiation, decreasing duration of radiation exposure, etc.

In addition, the intensity of the irradiation source (e.g., anultraviolet light source such as a mercury lamp) may be monitored with aphotodetector to detect a decrease of intensity from the irriadiationsource (e.g., through routine degredation thereof during use). Ifdetected, a process parameter may be adjusted through a controller toaccommodate the loss of intensity. Suitable process parameters for suchadjustment may include: increasing temperature with a heater, decreasingthe rate of advance of the carrier, increasing power to the lightsource, etc.

As another example, control of temperature and/or pressure to enhancefabrication time may be achieved with heaters and coolers (individually,or in combination with one another and separately responsive to acontroller), and/or with a pressure supply (e.g., pump, pressure vessel,valves and combinations thereof) and/or a pressure release mechanismsuch as a controllable valve (individually, or in combination with oneanother and separately responsive to a controller).

In some embodiments the controller is configured to maintain thegradient of polymerization zone described herein (see, e.g., FIG. 1)throughout the fabrication of some or all of the final product. Thespecific configuration (e.g., times, rate or speed of advancing,radiation intensity, temperature, etc.) will depend upon factors such asthe nature of the specific polymerizable liquid and the product beingcreated. Configuration to maintain the gradient of polymerization zonemay be carried out empirically, by entering a set of process parametersor instructions previously determined, or determined through a series oftest runs or “trial and error”; configuration may be provided throughpre-determined instructions; configuration may be achieved by suitablemonitoring and feedback (as discussed above), combinations thereof, orin any other suitable manner.

In some embodiments, a method and apparatus as described above may becontrolled by a software program running in a general purpose computerwith suitable interface hardware between that computer and the apparatusdescribed above. Numerous alternatives are commercially available.Non-limiting examples of one combination of components is shown in FIGS.3 to 5, where “Microcontroller” is Parallax Propeller, the Stepper MotorDriver is Sparkfun EasyDriver, the LED Driver is a Luxeon Single LEDDriver, the USB to Serial is a Parallax USB to Serial converter, and theDLP System is a Texas Instruments LightCrafter system.

4. General Methods

As noted above, the present invention provides a method of forming athree-dimensional object, comprising the steps of: (a) providing acarrier and a build plate, said build plate comprising a semipermeablemember, said semipermeable member comprising a build surface and a feedsurface separate from said build surface, with said build surface andsaid carrier defining a build region therebetween, and with said feedsurface in fluid contact with a polymerization inhibitor; then(concurrently and/or sequentially) (b) filing said build region with apolymerizable liquid, said polymerizable liquid contacting said buildsegment, (c) irradiating said build region through said build plate toproduce a solid polymerized region in said build region, with a liquidfilm release layer comprised of said polymerizable liquid formed betweensaid solid polymerized region and said build surface, the polymerizationof which liquid film is inhibited by said polymerization inhibitor; and(d) advancing said carrier with said polymerized region adhered theretoaway from said build surface on said stationary build plate to create asubsequent build region between said polymerized region and said topzone. In general the method includes (e) continuing and/or repeatingsteps (b) through (d) to produce a subsequent polymerized region adheredto a previous polymerized region until the continued or repeateddeposition of polymerized regions adhered to one another forms saidthree-dimensional object.

Since no mechanical release of a release layer is required, or nomechanical movement of a build surface to replenish oxygen is required,the method can be carried out in a continuous fashion, though it will beappreciated that the individual steps noted above may be carried outsequentially, concurrently, or a combination thereof. Indeed, the rateof steps can be varied over time depending upon factors such as thedensity and/or complexity of the region under fabrication.

Also, since mechanical release from a window or from a release layergenerally requires that the carrier be advanced a greater distance fromthe build plate than desired for the next irradiation step, whichenables the window to be recoated, and then return of the carrier backcloser to the build plate (e.g., a “two steps forward one step back”operation), the present invention in some embodiments permitselimination of this “back-up” step and allows the carrier to be advancedunidirectionally, or in a single direction, without intervening movementof the window for re-coating, or “snapping” of a pre-formed elasticrelease-layer. However, in other embodiments of the invention,reciprocation is utilized not for the purpose of obtaining release, butfor the purpose of more rapidly filling or pumping polymerizable liquidinto the build region.

In some embodiments, the advancing step is carried out sequentially inuniform increments (e.g., of from 0.1 or 1 microns, up to 10 or 100microns, or more) for each step or increment. In some embodiments, theadvancing step is carried out sequentially in variable increments (e.g.,each increment ranging from 0.1 or 1 microns, up to 10 or 100 microns,or more) for each step or increment. The size of the increment, alongwith the rate of advancing, will depend in part upon factors such astemperature, pressure, structure of the article being produced (e.g.,size, density, complexity, configuration, etc.)

In other embodiments of the invention, the advancing step is carried outcontinuously, at a uniform or variable rate.

In some embodiments, the rate of advance (whether carried outsequentially or continuously) is from about 0.1 1, or 10 microns persecond, up to about to 100, 1,000, or 10,000 microns per second, againdepending again depending on factors such as temperature, pressure,structure of the article being produced, intensity of radiation, etc

As described further below, in some embodiments the filling step iscarried out by forcing said polymerizable liquid into said build regionunder pressure. In such a case, the advancing step or steps may becarried out at a rate or cumulative or average rate of at least 0.1, 1,10, 50, 100, 500 or 1000 microns per second, or more. In general, thepressure may be whatever is sufficient to increase the rate of saidadvancing step(s) at least 2, 4, 6, 8 or 10 times as compared to themaximum rate of repetition of said advancing steps in the absence ofsaid pressure. Where the pressure is provided by enclosing an apparatussuch as described above in a pressure vessel and carrying the processout in a pressurized atmosphere (e.g., of air, air enriched with oxygen,a blend of gasses, pure oxygen, etc.) a pressure of 10, 20, 30 or 40pounds per square inch (PSI) up to, 200, 300, 400 or 500 PSI or more,may be used. For fabrication of large irregular objects higher pressuresmay be less preferred as compared to slower fabrication times due to thecost of a large high pressure vessel. In such an embodiment, both thefeed surface and the polymerizable liquid can be are in fluid contactwith the same compressed gas (e.g., one comprising from 20 to 95 percentby volume of oxygen, the oxygen serving as the polymerization inhibitor.

On the other hand, when smaller items are fabricated, or a rod or fiberis fabricated that can be removed or exited from the pressure vessel asit is produced through a port or orifice therein, then the size of thepressure vessel can be kept smaller relative to the size of the productbeing fabricated and higher pressures can (if desired) be more readilyutilized.

As noted above, the irradiating step is in some embodiments carried outwith patterned irradiation. The patterned irradiation may be a fixedpattern or may be a variable pattern created by a pattern generator(e.g., a DLP) as discussed above, depending upon the particular itembeing fabricated.

When the patterned irradiation is a variable pattern rather than apattern that is held constant over time, then each irradiating step maybe any suitable time or duration depending on factors such as theintensity of the irradiation, the presence or absence of dyes in thepolymerizable material, the rate of growth, etc. Thus in someembodiments each irradiating step can be from 0.001, 0.01, 0.1, 1 or 10microseconds, up to 1, 10, or 100 minutes, or more, in duration. Theinterval between each irradiating step is in some embodiments preferablyas brief as possible, e.g., from 0.001, 0.01, 0.1, or 1 microseconds upto 0.1, 1, or 10 seconds.

While the dead zone and the gradient of polymerization zone do not havea strict boundary therebetween (in those locations where the two meet),the thickness of the gradient of polymerization zone is in someembodiments at least as great as the thickness of the dead zone. Thus,in some embodiments, the dead zone has a thickness of from 0.01, 0.1, 1,2, or 10 microns up to 100, 200 or 400 microns, or more, and/or saidgradient of polymerization zone and said dead zone together have athickness of from 1 or 2 microns up to 400, 600, or 1000 microns, ormore. Thus the gradient of polymerization zone may be thick or thindepending on the particular process conditions at that time. Where thegradient of polymerization zone is thin, it may also be described as anactive surface on the bottom of the growing three-dimensional object,with which monomers can react and continue to form growing polymerchains therewith. In some embodiments, the gradient of polymerizationzone, or active surface, is maintained (while polymerizing stepscontinue) for a time of at least 5, 10, 15, 20 or 30 seconds, up to 5,10, 15 or 20 minutes or more, or until completion of thethree-dimensional product.

The method may further comprise the step of disrupting said gradient ofpolymerization zone for a time sufficient to form a cleavage line insaid three-dimensional object (e.g., at a predetermined desired locationfor intentional cleavage, or at a location in said object whereprevention of cleavage or reduction of cleavage is non-critical), andthen reinstating said gradient of polymerization zone (e.g. by pausing,and resuming, the advancing step, increasing, then decreasing, theintensity of irradiation, and combinations thereof

In some embodiments the build surface is flat; in other the buildsurface is irregular such as convexly or concavely curved, or has wallsor trenches formed therein. In either case the build surface may besmooth or textured.

Curved and/or irregular build plates or build surfaces can be used infiber or rod formation, to provide different materials to a singleobject being fabricated (that is, different polymerizable liquids to thesame build surface through channels or trenches formed in the buildsurface, each associated with a separate liquid supply, etc.

Carrier Feed Channels for Polymerizable liquid. While polymerizableliquid may be provided directly to the build plate from a liquid conduitand reservoir system, in some embodiments the carrier include one ormore feed channels therein. The carrier feed channels are in fluidcommunication with the polymerizable liquid supply, for example areservoir and associated pump. Different carrier feed channels may be influid communication with the same supply and operate simultaneously withone another, or different carrier feed channels may be separatelycontrollable from one another (for example, through the provision of apump and/or valve for each). Separately controllable feed channels maybe in fluid communication with a reservoir containing the samepolymerizable liquid, or may be in fluid communication with a reservoircontaining different polymerizable liquids. Through the use of valveassemblies, different polymerizable liquids may in some embodiments bealternately fed through the same feed channel, if desired.

5. Reciprocating Feed of Polymerizable Liquid

In an embodiment of the present invention, the carrier is verticallyreciprocated with respect to the build surface to enhance or speed therefilling of the build region with the polymerizable liquid.

In some embodiments, the vertically reciprocating step, which comprisesan upstroke and a downstroke, is carried out with the distance of travelof the upstroke being greater than the distance of travel of thedownstroke, to thereby concurrently carry out the advancing step (thatis, driving the carrier away from the build plate in the Z dimension) inpart or in whole.

In some embodiments, the speed of the upstroke gradually accelerates(that is, there is provided a gradual start and/or gradual accelerationof the upstroke, over a period of at least 20, 30, 40, or 50 percent ofthe total time of the upstroke, until the conclusion of the upstroke, orthe change of direction which represents the beginning of thedownstroke. Stated differently, the upstroke begins, or starts, gentlyor gradually.

In some embodiments, the speed of the downstroke gradually decelerates(that is, there is provided a gradual termination and/or gradualdeceleration of the downstroke, over a period of at least 20, 30, 40, or50 percent of the total time of the downstroke. Stated differently, thedownstroke concludes, or ends, gently or gradually.

While in some embodiments there is an abrupt end, or abruptdeceleration, of the upstroke, and an abrupt beginning or decelerationof the downstroke (e.g., a rapid change in vector or direction of travelfrom upstroke to downstroke), it will be appreciated that gradualtransitions may be introduced here as well (e.g., through introductionof a “plateau” or pause in travel between the upstroke and downstroke).It will also be appreciated that, while each reciprocating step may beconsist of a single upstroke and downstroke, the reciprocation step maycomprise a plurality of 2, 3, 4 or 5 or more linked set ofreciprocations, which may e the same or different in frequent and/oramplitude

In some embodiments, the vertically reciprocating step is carried outover a total time of from 0.01 or 0.1 seconds up to 1 or 10 seconds(e.g., per cycle of an upstroke and a downstroke).

In some embodiments, the upstroke distance of travel is from 0.02 or 0.2millimeters (or 20 or 200 microns) to 1 or 10 millimeters (or 1000 to10,000 microns). The distance of travel of the downstroke may be thesame as, or less than, the distance of travel of the upstroke, where alesser distance of travel for the downstroke serves to achieve theadvancing of the carrier away from the build surface as thethree-dimensional object is gradually formed. Where a reciprocation stepcomprises multiple linked reciprocations, the sum distance of travel ofall upstrokes in that set is preferably greater than the sum distance oftravel of all downstrokes in that set, to achieve the advancing of thecarrier away from the build surface as the three-dimensional object isgradually formed.

Preferably the vertically reciprocating step, and particularly theupstroke thereof, does not cause the formation of gas bubbles or a gaspocket in the build region, but instead the build region remains filledwith the polymerizable liquid throughout the reciprocation steps, andthe gradient of polymerization zone or region remains in contact withthe “dead zone” and with the growing object being fabricated throughoutthe reciprocation steps. As will be appreciated, a purpose of thereciprocation is to speed or enhance the refilling of the build region,particularly where larger build regions are to be refilled withpolymerizable liquid, as compared to the speed at which the build regioncould be refilled without the reciprocation step.

In some embodiments, the advancing step is carried out intermittently ata rate of 1, 2, 5 or 10 individual advances per minute up to 300, 600,or 1000 individual advances per minute, each followed by a pause duringwhich an irradiating step is carried out. It will be appreciated thatone or more reciprocation steps (e.g., upstroke plus downstroke) may becarried out within each advancing step. Stated differently, thereciprocating steps may be nested within the advancing steps.

In some embodiments, the individual advances are carried out over anaverage distance of travel for each advance of from 10 or 50 microns to100 or 200 microns (optionally including the total distance of travelfor each vertically reciprocating step, e.g., the sum of the upstrokedistance minus the downstroke distance).

Apparatus for carrying out the invention in which the reciprocationsteps described herein are implemented substantially as described above,with the drive associated with the carrier, and/or with an additionaldrive operatively associated with the transparent member, and with thecontroller operatively associated with either or both thereof andconfigured to reciprocate the carrier and transparent member withrespect to one another as described above.

6. Increased Speed of Fabrication by Increasing Light Intensity

In general, it has been observed that speed of fabrication can increasewith increased light intensity. In some embodiments, the light isconcentrated or “focused” at the build region to increase the speed offabrication. This may be accomplished using an optical device such as anobjective lens.

The speed of fabrication may be generally proportional to the lightintensity. For example, the build speed in millimeters per hour may becalculated by multiplying the light intensity in milliWatts per squarecentimeter and a multiplier. The multiplier may depend on a variety offactors, including those discussed below. A range of multipliers, fromlow to high, may be employed. On the low end of the range, themultiplier may be about 10, 15, 20 or 30. On the high end of themutipler range, the multiplier may be about 150, 300, 400 or more.

The relationships described above are, in general, contemplated forlight intensities of from 1, 5 or 10 milliWatts per square centimeter,up to 20 or 50 milliWatts per square centimeter.

Certain optical characteristics of the light may be selected tofacilitate increased speed of fabrication. By way of example, a bandpass filter may be used with a mercury bulb light source to provide365±10 nm light measured at Full Width Half Maximum (FWHM). By way offurther example, a band pass filter may be used with an LED light sourceto provide 375±15 nm light measured at FWHM.

As noted above, poymerizable liquids used in such processes are, ingeneral, free radical polymerizable liquids with oxygen as theinhibitor, or acid-catalyzed or cationically polymerizable liquids witha base as the inhibitor. Some specific polymerizable liquids will ofcourse cure more rapidly or efficiently than others and hence be moreamenable to higher speeds, though this may be offset at least in part byfurther increasing light intensity.

At higher light intensities and speeds, the “dead zone” may becomethinner as inhibitor is consumed. If the dead zone is lost then theprocess will be disrupted. In such case, the supply of inhibitor may beenhanced by any suitable means, including providing an enriched and/orpressurized atmosphere of inhibitor, a more porous semipermeable member,a stronger or more powerful inhibitor (particularly where a base isemployed), etc.

In general, lower viscosity polymerizable liquids are more amenable tohigher speeds, particularly for fabrication of articles with a largeand/or dense cross section (although this can be offset at least in partby increasing light intensity). Polymerizable liquids with viscositiesin the range of 50 or 100 centipoise, up to 600, 800 or 1000 centipoiseor more (as measured at room temperature and atmospheric pressure with asuitable device such as a HYDRAMOTION REACTAVISC™ Viscometer (availablefrom Hydramotion Ltd, 1 York Road Business Park, Malton, York Y017 6YAEngland). In some embodiments, where necessary, the viscosity of thepolymerizable liquid can advantageously be reduced by heating thepolymerizable liquid, as described above.

In some embodiments, such as fabrication of articles with a large and/ordense cross-section, speed of fabrication can be enhanced by introducingreciprocation to “pump” the polymerizable liquid, as described above,and/or the use of feeding the polymerizable liquid through the carrier,as also described above, and/or heating and/or pressurizing thepolymerizable liquid, as also described above.

7. Tiling

It may be desirable to use more than one light engine to preserveresolution and light intensity for larger build sizes. Each light enginemay be configured to project an image (e.g., an array of pixels) intothe build region such that a plurality of “tiled” images are projectedinto the build region. As used herein, the term “light engine” can meanan assembly including a light source, a DLP device such as a digitalmicromirror device and an optical device such as an objective lens. The“light engine” may also include electronics such as a controller that isoperatively associated with one or more of the other components.

In some embodiments, the configuration with the overlapped images isemployed with some form of “blending” or “smoothing” of the overlappedregions as generally discussed in, for example, U.S. Pat. Nos.7,292,207, 8,102,332, 8,427,391, 8,446,431 and U.S. Patent ApplicationPublication Nos. 2013/0269882, 2013/0278840 and 2013/0321475, thedisclosures of which are incorporated herein in their entireties.

The tiled images can allow for larger build areas without sacrificinglight intensity, and therefore can facilitate faster build speeds forlarger objects. It will be understood that more than two light engineassemblies (and corresponding tiled images) may be employed. Variousembodiments of the invention employ at least 4, 8, 16, 32, 64, 128 ormore tiled images.

8. Fabrication in Multiple Zones

As noted above, embodiments of the invention may carry out the formationof the three-dimensional object through multiple zones or segments ofoperation. Such a method generally comprises:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween, with the carrier positioned adjacent and spaced apart fromthe build surface at a start position; then

(b) forming an adhesion segment of the three-dimensional object by:

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) irradiating the build region with light through the        optically transparent member (e.g., by a single exposure), while    -   (iii) maintaining the carrier stationary or advancing the        carrier away from the build surface at a first cumulative rate        of advance, to thereby form from the polymerizable liquid a        solid polymer adhesion segment of the object adhered to the        carrier; then

(c) optionally but preferably forming a transition segment of the threedimensional object by

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) continuously or intermittently irradiating the build region        with light through the optically transparent member, and    -   (iii) continuously or intermittently advancing (e.g.,        sequentially or concurrently with the irradiating step) the        carrier away from the build surface at a second cumulative rate        of advance to thereby form from the polymerizable liquid a        transition segment of the object between the adhesion segment        and the build surface;    -   wherein the second cumulative rate of advance is greater than        the first cumulative rate of advance; and then

(d) forming a body segment of the three dimensional object by:

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) continuously or intermittently irradiating the build region        with light through the optically transparent, and    -   (iii) continuously or intermittently advancing (e.g.,        sequentially or concurrently with the irradiating step) the        carrier away from the build surface at a third cumulative rate        of advance, to thereby form from the polymerizable liquid a body        segment of the object between the transition segment and the        build surface;    -   wherein the third cumulative rate of advance is greater than the        first and/or the second cumulative rate of advance.

Note that the start position can be any position among a range ofpositions (e.g., a range of up to 5 or 10 millimeters or more), and theirradiating step (b) (ii) is carried out at an intensity sufficient toadhere the solid polymer to the carrier when the carrier is at anyposition within that range of positions. This advantageously reduces thepossibility of failure of adhesion of the three-dimensional object tothe carrier due to variations in uniformity of the carrier and/or buildsurfaces, variations inherent in drive systems in positioning thecarrier adjacent the build surface, etc.

9. Fabrication with Intermittent (or Strobe”) Illumination

As noted above, in some embodiments the invention may be carried outwith the illumination in intermittent periods or burst. In oneembodiment, such a method comprises:

providing a carrier and an optically transparent member having a buildsurface, the carrier and the build surface defining a build regiontherebetween;

filling the build region with a polymerizable liquid,

intermittently irradiating the build region with light through theoptically transparent member to form a solid polymer from thepolymerizable liquid,

continuously advancing the carrier away from the build surface to formthe three-dimensional object from the solid polymer.

Another embodiment of such a mode of operation comprises:

providing a carrier and an optically transparent member having a buildsurface, the carrier and the build surface defining a build regiontherebetween;

filling the build region with a polymerizable liquid,

intermittently irradiating the build region with light through theoptically transparent member to form a solid polymer from thepolymerizable liquid,

continuously or intermittently advancing (e.g., sequentially orconcurrently with the irradiating step) the carrier away from the buildsurface to form the three-dimensional object from the solid polymer.

In some embodiments, the intermittently irradiating comprisesalternating periods of active and inactive illumination, where theaverage duration of the periods of active illumination is less than theaverage duration of the periods of inactive illumination (e.g., is notmore than 50, 60, or 80 percent thereof).

In other embodiments, the intermittently irradiating comprisesalternating periods of active and inactive illumination, where theaverage duration of the periods of active illumination is the same as orgreater than the average duration of the periods of inactiveillumination (e.g., is at least 100, 120, 160, or 180 percent thereof).

Examples of such modes of operation are given further below. Thesefeatures may be combined with any of the other features and operatingsteps or parameters described herein.

10. Dual Hardening Polymerizable Liquids: Part B

As noted above, in some embodiments of the invention, the polymerizableliquid comprises a first light polymerizable component (sometimesreferred to as “Part A” herein) and a second component that solidifiesby another mechanism, or in a different manner from, the first component(sometimes referred to as “Part B” herein), typically by furtherreacting, polymerizing, or chain extending. Numerous embodiments thereofmay be carried out. In the following, note that, where particularacrylates such as methacrylates are described, other acrylates may alsobe used.

Part A chemistry. As noted above, in some embodiments of the presentinvention, a resin will have a first component, termed “Part A.” Part Acomprises or consists of a mix of monomers and/or prepolymers that canbe polymerized by exposure to actinic radiation or light. This resin canhave a functionality of 2 or higher (though a resin with a functionalityof 1 can also be used when the polymer does not dissolve in itsmonomer). A purpose of Part A is to “lock” the shape of the object beingformed or create a scaffold for the one or more additional components(e.g., Part B). Importantly, Part A is present at or above the minimumquantity needed to maintain the shape of the object being formed afterthe initial solidification. In some embodiments, this amount correspondsto less than ten, twenty, or thirty percent by weight of the total resin(polymerizable liquid) composition.

In some embodiments, Part A can react to form a cross-linked polymernetwork or a solid homopolymer.

Examples of suitable reactive end groups suitable for Part Aconstituents, monomers, or prepolymers include, but are not limited to:acrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

An aspect of the solidification of Part A is that it provides a scaffoldin which a second reactive resin component, termed “Part B,” cansolidify during a second step (which may occur concurrently with orfollowing the solidification of Part A). This secondary reactionpreferably occurs without significantly distorting the original shapedefined during the solidification of Part A. Alternative approacheswould lead to a distortion in the original shape in a desired manner.

In particular embodiments, when used in the methods and apparatusdescribed herein, the solidification of Part A is continuously inhibitedduring printing within a certain region, by oxygen or amines or otherreactive species, to form a liquid interface between the solidified partand an inhibitor-permeable film or window (e.g., is carried out bycontinuous liquid interphase/interface printing).

Part B chemistry. Part B may comprise, consist of or consist essentiallyof a mix of monomers and/or prepolymers that possess reactive end groupsthat participate in a second solidification reaction after the Part Asolidification reaction. In some embodiments, Part B could be addedsimultaneously to Part A so it is present during the exposure toactinide radiation, or Part B could be infused into the object madeduring the 3D printing process in a subsequent step. Examples of methodsused to solidify Part B include, but are not limited to, contacting theobject or scaffold to heat, water or water vapor, light at a differentwavelength than that at which Part A is cured, catalysts, (with orwithout additional heat), evaporation of a solvent from thepolymerizable liquid (e.g., using heat, vacuum, or a combinationthereof), microwave irradiation, etc., including combinations thereof.

Examples of suitable reactive end group pairs suitable for Part Bconstituents, monomers or prepolymers include, but are not limited to:epoxy/amine, epoxy/hydroxyl, oxetane/amine, oxetane/alcohol,isocyanate*/hydroxyl, Isocyanate*/amine, isocyanate/carboxylic acid,anhydride/amine, amine/carboxylic acid, amine/ester, hydroxyl/carboxylicacid, hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H(hydrosilylation), Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde,amine/aldehyde, hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast,alkyne/Azide (also known as one embodiment of “Click Chemistry,” alongwith additional reactions including thiolene, Michael additions,Diels-Alder reactions, nucleophilic substitution reactions, etc.),alkene/Sulfur (polybutadiene vulcanization), alkene/peroxide,alkene/thiol, alkyne/thiol, hydroxyl/halide, isocyanate*/water(polyurethane foams), Si—OH/hydroxyl, Si—OH/water, Si—OH/Si—H (tincatalyzed silicone), Si—OH/Si—OH (tin catalyzed silicone),Perfluorovinyl (coupling to form perfluorocyclobutane), etc., where*Isocyanates include protected isocyanates (e.g. oximes)),diene/dienophiles for Diels-Alder reactions, olefin metathesispolymerization, olefin polymerization using Ziegler-Natta catalysis,ring-opening polymerization (including ring-opening olefin metathesispolymerization, lactams, lactones, Siloxanes, epoxides, cyclic ethers,imines, cyclic acetals, etc.), etc.

Other reactive chemistries suitable for Part B will be recognizable bythose skilled in the art. Part B components useful for the formation ofpolymers described in “Concise Polymeric Materials Encyclopedia” and the“Encyclopedia of Polymer Science and Technology” are hereby incorporatedby reference.

Organic peroxides. In some embodiments, an organic peroxide may beincluded in the polymerizable liquid or resin, for example to facilitatethe reaction of potentially unreacted double bonds during heat and/ormicrowave irradiation curing. Such organic peroxides may be included inthe resin or polymerizable liquid in any suitable amount, such as from0.001 or 0.01 or 0.1 percent by weight, up to 1, 2, or 3 percent byweight. Examples of suitable organic peroxides include, but are notlimited to, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (e.g., LUPEROX101™), dilauroyl peroxide (e.g. LUPEROX LP™) benzoyl peroxide (e.g.,LUPEROX A98™), and bis(tert-butyldioxyisopropyl)benzene (e.g., VulCUPR™), etc., including combinations thereof. Such organic peroxides areavailable from a variety of sources, including but not limited to Arkema(420 rue d'Estienne d'Orves, 92705 Colombes Cedex, France).

Elastomers. A particularly useful embodiment for implementing theinvention is for the formation of elastomers. Tough, high-elongationelastomers are difficult to achieve using only liquid UV-curableprecursors. However, there exist many thermally cured materials(polyurethanes, silicones, natural rubber) that result in tough,high-elongation elastomers after curing. These thermally curableelastomers on their own are generally incompatible with most 3D printingtechniques.

In embodiments of the current invention, small amounts (e.g., less than20 percent by weight) of a low-viscosity UV curable material (Part A)are blended with thermally-curable precursors to form (preferably tough)elastomers (e.g. polyurethanes, polyureas, or copolymers thereof (e.g.,poly(urethane-urea)), and silicones) (Part B). The UV curable componentis used to solidify an object into the desired shape using 3D printingas described herein and a scaffold for the elastomer precursors in thepolymerizable liquid. The object can then be heated after printing,thereby activating the second component, resulting in an objectcomprising the elastomer.

Adhesion of formed objects. In some embodiments, it may be useful todefine the shapes of multiple objects using the solidification of PartA, align those objects in a particular configuration, such that there isa hermetic seal between the objects, then activate the secondarysolidification of Part B. In this manner, strong adhesion between partscan be achieved during production. A particularly useful example may bein the formation and adhesion of sneaker components.

Fusion of particles as Part B. In some embodiments, “Part B” may simplyconsist of small particles of a pre-formed polymer. After thesolidification of Part A, the object may be heated above the glasstransition temperature of Part B in order to fuse the entrappedpolymeric particles.

Evaporation of solvent as Part B. In some embodiments, “Part B” mayconsist of a pre-formed polymer dissolved in a solvent. After thesolidification of Part A into the desired object, the object issubjected to a process (e.g. heat+vacuum) that allows for evaporation ofthe solvent for Part B, thereby solidifying Part B.

Thermally cleavable end groups. In some embodiments, the reactivechemistries in Part A can be thermally cleaved to generate a newreactive species after the solidification of Part A. The newly formedreactive species can further react with Part B in a secondarysolidification. An exemplary system is described by Velankar, Pezos andCooper, Journal of Applied Polymer Science, 62, 1361-1376 (1996). Here,after UV-curing, the acrylate/methacrylate groups in the formed objectare thermally cleaved to generated diisocyanate prepolymers that furtherreact with blended chain-extender to give high molecular weightpolyurethanes/polyureas within the original cured material or scaffold.Such systems are, in general, dual-hardening systems that employ blockedor reactive blocked prepolymers, as discussed in greater detail below.It may be noted that later work indicates that the thermal cleavageabove is actually a displacement reaction of the chain extender (usuallya diamine) with the hindered urea, giving the finalpolyurethanes/polyureas without generating isocyanate intermediates.

Methods of mixing components. In some embodiments, the components may bemixed in a continuous manner prior to being introduced to the printerbuild plate. This may be done using multi-barrel syringes and mixingnozzles. For example, Part A may comprise or consist of a UV-curabledi(meth)acrylate resin, Part B may comprise or consist of a diisocyanateprepolymer and a polyol mixture. The polyol can be blended together inone barrel with Part A and remain unreacted. A second syringe barrelwould contain the diisocyanate of Part B. In this manner, the materialcan be stored without worry of “Part B” solidifying prematurely.Additionally, when the resin is introduced to the printer in thisfashion, a constant time is defined between mixing of all components andsolidification of Part A.

Additional examples of “dual cure” polymerizable liquids (or “resins”),and methods that may be used in carrying out the present inventioninclude, but are not limited to, those set forth in J. Rolland et al.,Method of Producing Polyurethane Three-Dimensional Objects fromMaterials having Multiple Mechanisms of Hardening, PCT Publication No.WO 2015/200179 (published 30 Dec. 2015); J. Rolland et al., Methods ofProducing Three-Dimensional Objects from Materials Having MultipleMechanisms of Hardening, PCT Publication No. WO 2015/200173 (published30 Dec. 2015); J. Rolland et al., Three-Dimensional Objects Producedfrom Materials Having Multiple Mechanisms of Hardening, PCT PublicationNo. WO/2015/200189 (published 30 Dec. 2015); J. Rolland et al.,Polyurethane Resins Having Multiple Mechanisms of Hardening for Use inProducing Three-Dimensional Objects published 30 Dec. 2015); and

J. Rolland et al., Method of Producing Three-Dimensional Objects fromMaterials having Multiple Mechanisms of Hardening, U.S. patentapplication Ser. No. 14/977,822 (filed 22 Dec. 2015); J. Rolland et al.,Method of Producing Polyurethane Three-Dimensional Objects fromMaterials having Multiple Mechanisms of Hardening, U.S. patentapplication Ser. No. 14/977,876 (filed 22 Dec. 2015), J. Rolland et al.,Three-Dimensional Objects Produced from Materials having MultipleMechanisms of Hardening, U.S. patent application Ser. No. 14/977,938(filed 22 Dec. 2015), and J. Rolland et al., Polyurethane Resins havingMultiple Mechanisms of Hardening for Use in Producing Three-DimensionalObjects, U.S. patent application Ser. No. 14/977,974 (filed 22 Dec.2015);

the disclosures of all of which are incorporated by reference herein intheir entirety.

11. Fabrication Products

Three-dimensional products produced by the methods and processes of thepresent invention may be final, finished or substantially finishedproducts, or may be intermediate products subject to furthermanufacturing steps such as surface treatment, laser cutting, electricdischarge machining, etc., is intended. Intermediate products includeproducts for which further additive manufacturing, in the same or adifferent apparatus, may be carried out). For example, a fault orcleavage line may be introduced deliberately into an ongoing “build” bydisrupting, and then reinstating, the gradient of polymerization zone,to terminate one region of the finished product, or simply because aparticular region of the finished product or “build” is less fragilethan others.

Numerous different products can be made by the methods and apparatus ofthe present invention, including both large-scale models or prototypes,small custom products, miniature or microminiature products or devices,etc. Examples include, but are not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,functional structures, microneedle arrays, fibers and rods such aswaveguides, micromechanical devices, microfluidic devices, etc.

Thus in some embodiments the product can have a height of from 0.1 or 1millimeters up to 10 or 100 millimeters, or more, and/or a maximum widthof from 0.1 or 1 millimeters up to 10 or 100 millimeters, or more. Inother embodiments, the product can have a height of from 10 or 100nanometers up to 10 or 100 microns, or more, and/or a maximum width offrom 10 or 100 nanometers up to 10 or 100 microns, or more. These areexamples only: Maximum size and width depends on the architecture of theparticular device and the resolution of the light source and can beadjusted depending upon the particular goal of the embodiment or articlebeing fabricated.

In some embodiments, the ratio of height to width of the product is atleast 2:1, 10:1, 50:1, or 100:1, or more, or a width to height ratio of1:1, 10:1, 50:1, or 100:1, or more.

In some embodiments, the product has at least one, or a plurality of,pores or channels formed therein, as discussed further below.

The processes described herein can produce products with a variety ofdifferent properties. Hence in some embodiments the products are rigid;in other embodiments the products are flexible or resilient. In someembodiments, the products are a solid; in other embodiments, theproducts are a gel such as a hydrogel. In some embodiments, the productshave a shape memory (that is, return substantially to a previous shapeafter being deformed, so long as they are not deformed to the point ofstructural failure). In some embodiments, the products are unitary (thatis, formed of a single polymerizable liquid); in some embodiments, theproducts are composites (that is, formed of two or more differentpolymerizable liquids). Particular properties will be determined byfactors such as the choice of polymerizable liquid(s) employed.

In some embodiments, the product or article made has at least oneoverhanging feature (or “overhang”), such as a bridging element betweentwo supporting bodies, or a cantilevered element projecting from onesubstantially vertical support body. Because of the unidirectional,continuous nature of some embodiments of the present processes, theproblem of fault or cleavage lines that form between layers when eachlayer is polymerized to substantial completion and a substantial timeinterval occurs before the next pattern is exposed, is substantiallyreduced. Hence, in some embodiments the methods are particularlyadvantageous in reducing, or eliminating, the number of supportstructures for such overhangs that are fabricated concurrently with thearticle.

12. Additional and Alternate Methods and Apparatus

Additional examples of apparatus, polymerizable liquids (or “resins”),and methods that may be used in carrying out the present inventioninclude, but are not limited to, those set forth in J. DeSimone et al.,Three-Dimensional Printing Using Tiled Light Engines, PCT PublicationNo. WO/2015/195909 (published 23 Dec. 2015); J. DeSimone et al.,Three-Dimensional Printing Method Using Increased Light Intensity andApparatus Therefore, PCT Publication No. WO/2015/195920 (published 23Dec. 2015), A. Ermoshkin et al., Three-Dimensional Printing withReciprocal Feeding of Polymerizable Liquid, PCT Publication No.WO/2015/195924 (published 23 Dec. 2015); J. Rolland et al., Method ofProducing Polyurethane Three-Dimensional Objects from Materials havingMultiple Mechanisms of Hardening, PCT Publication No. WO 2015/200179(published 30 Dec. 2015); J. Rolland et al., Methods of ProducingThree-Dimensional Objects from Materials Having Multiple Mechanisms ofHardening, PCT Publication No. WO 2015/200173 (published 30 Dec. 2015);J. Rolland et al., Three-Dimensional Objects Produced from MaterialsHaving Multiple Mechanisms of Hardening, PCT Publication No.WO/2015/200189 (published 30 Dec. 2015); J. Rolland et al., PolyurethaneResins Having Multiple Mechanisms of Hardening for Use in ProducingThree-Dimensional Objects published 30 Dec. 2015); and J. DeSimone etal., Methods and Apparatus for Continuous Liquid Interface Productionwith Rotation, PCT Publication No. WO/2016/007495, the disclosures ofwhich are incorporated by reference herein in their entirety.

In an alternate embodiment of the invention, the methods may be carriedout with a method and apparatus as described in Hull, U.S. Pat. No.5,236,637, at FIG. 4, where the polymerizable liquid is floated on topof an immiscible liquid layer (said to be “non-wetting” therein). Here,the immiscible liquid layer serves as the build surface. If soimplemented, the immiscible liquid (which may be aqueous or non-aqueous)preferably: (i) has a density greater than the polymerizable liquid,(ii) is immiscible with the polymerizable liquid, and (iii) is wettablewith the polymerizable liquid. Ingredients such as surfactants, wettingagents, viscosity-enhancing agents, pigments, and particles mayoptionally be included in either or both of the polymerizable liquid orimmiscible liquid.

While the present invention is preferably carried out by continuousliquid interphase polymerization, as described in detail above, in someembodiments alternate methods and apparatus for bottom-upthree-dimension fabrication may be used, including layer-by-layerfabrication. Examples of such methods and apparatus include, but are notlimited to, those described U.S. Pat. No. 7,438,846 to John and U.S.Pat. No. 8,110,135 to El-Siblani, and in U.S. Patent ApplicationPublication Nos. 2013/0292862 to Joyce and 2013/0295212 to Chen et al.The disclosures of these patents and applications are incorporated byreference herein in their entirety.

The present invention is explained in greater detail in the followingnon-limiting Examples.

EXAMPLE 1 Continuous Fabrication with Intermittent Irradiation andAdvancing

A process of the present invention is illustrated in FIG. 6, where thevertical axis illustrates the movement of the carrier away from thebuild surface. In this embodiment, the vertical movement or advancingstep (which can be achieved by driving either the carrier or the buildsurface, preferably the carrier), is continuous and unidirectional, andthe irradiating step is carried out continuously. Polymerization of thearticle being fabricated occurs from a gradient of polymerization, andhence creation of “layer by layer” fault lines within the article isminimized.

An alternate embodiment of the present invention is illustrated in FIG.7. In this embodiment, the advancing step is carried out in astep-by-step manner, with pauses introduced between active advancing ofthe carrier and build surface away from one another. In addition, theirradiating step is carried out intermittently, in this case during thepauses in the advancing step. We find that, as long as the inhibitor ofpolymerization is supplied to the dead zone in an amount sufficient tomaintain the dead zone and the adjacent gradient of polymerizationduring the pauses in irradiation and/or advancing, the gradient ofpolymerization is maintained, and the formation of layers within thearticle of manufacture is minimized or avoided. Stated differently, thepolymerization is continuous, even though the irradiating and advancingsteps are not. Sufficient inhibitor can be supplied by any of a varietyof techniques, including but not limited to: utilizing a transparentmember that is sufficiently permeable to the inhibitor, enriching theinhibitor (e.g., feeding the inhibitor from an inhibitor-enriched and/orpressurized atmosphere), etc. In general, the more rapid the fabricationof the three-dimensional object (that is, the more rapid the cumulativerate of advancing), the more inhibitor will be required to maintain thedead zone and the adjacent gradient of polymerization.

EXAMPLE 2 Continuous Fabrication with Reciprocation During Advancing toEnhance Filling of Build Region with Polymerizable Liquid

A still further embodiment of the present invention is illustrated inFIG. 8. As in Example 1, FIG. 7, above, this embodiment, the advancingstep is carried out in a step-by-step manner, with pauses introducedbetween active advancing of the carrier and build surface away from oneanother. Also as in Example 1 above, the irradiating step is carried outintermittently, again during the pauses in the advancing step. In thisexample, however, the ability to maintain the dead zone and gradient ofpolymerization during the pauses in advancing and irradiating is takenadvantage of by introducing a vertical reciprocation during the pausesin irradiation.

We find that vertical reciprocation (driving the carrier and buildsurface away from and then back towards one another), particularlyduring pauses in irradiation, serves to enhance the filling of the buildregion with the polymerizable liquid, apparently by pullingpolymerizable liquid into the build region. This is advantageous whenlarger areas are irradiated or larger parts are fabricated, and fillingthe central portion of the build region may be rate-limiting to anotherwise rapid fabrication.

Reciprocation in the vertical or Z axis can be carried out at anysuitable speed in both directions (and the speed need not be the same inboth directions), although it is preferred that the speed whenreciprocating away is insufficient to cause the formation of gas bubblesin the build region.

While a single cycle of reciprocation is shown during each pause inirradiation in FIG. 23, it will be appreciated that multiple cycles(which may be the same as or different from one another) may beintroduced during each pause.

As in Example 1 above, as long as the inhibitor of polymerization issupplied to the dead zone in an amount sufficient to maintain the deadzone and the adjacent gradient of polymerization during thereciprocation, the gradient of polymerization is maintained, theformation of layers within the article of manufacture is minimized oravoided, and the polymerization/fabrication remains continuous, eventhough the irradiating and advancing steps are not.

EXAMPLE 3 Acceleration During Reciprocation Upstroke and DecelerationDuring Reciprocation Downstroke to Enhance Part Quality

We observe that there is a limiting speed of upstroke, and correspondingdownstroke, which if exceeded causes a deterioration of quality of thepart or object being fabricated (possibly due to degradation of softregions within the gradient of polymerization caused by lateral shearforces a resin flow). To reduce these shear forces and/or enhance thequality of the part being fabricated, we introduce variable rates withinthe upstroke and downstroke, with gradual acceleration occurring duringthe upstroke and gradual deceleration occurring during the downstroke,as schematically illustrated in FIG. 9.

EXAMPLE 4 Fabrication in Multiple Zones

FIG. 10 schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object bymethods as described above, through a first base (or “adhesion”) zone,an optional second transition zone, and a third body zone. The overallprocess of forming the three-dimensional object is thus divided intothree (or two) immediately sequential segments or zones. The zones arepreferably carried out in a continuous sequence without pausesubstantial delay (e.g., greater than 5 or 10 seconds) between the threezones, preferably so that the gradient of polymerization is notdisrupted between the zones.

The first base (or “adhesion”) zone includes an initial light orirradiation exposure at a higher dose (longer duration and/or greaterintensity) than used in the subsequent transition and/or body zones.This is to obviate the problem of the carrier not being perfectlyaligned with the build surface, and/or the problem of variation in thepositioning of the carrier from the build surface, at the start of theprocess, by insuring that the resin is securely polymerized to thecarrier. Note an optional reciprocation step (for initial distributingor pumping of the polymerizable liquid in or into the build region) isshown before the carrier is positioned in its initial, start, position.Note that a release layer (not shown) such as a soluble release layermay still be included between the carrier and the initial polymerizedmaterial, if desired. In general, a small or minor portion of thethree-dimensional object is produced during this base zone (e.g., lessthan 1, 2 or 5 percent by volume). Similarly, the duration of this basezone is, in general, a small or minor portion of the sum of thedurations of the base zone, the optional transition zone, and the bodyzone (e.g., less than 1, 2 or 5 percent).

Immediately following the first base zone of the process, there isoptionally (but preferably) a transition zone. In this embodiment, theduration and/or intensity of the illumination is less, and thedisplacement of the oscillatory step less, compared to that employed inthe base zone as described above. The transition zone may (in theillustrated embodiment) proceed through from 2 or 5, up to 50 or moreoscillatory steps and their corresponding illuminations. In general, anintermediate portion (greater than that formed during the base zone, butless than that formed of during the body zone), of the three dimensionalobject is produced during the transition zone (e.g., from 1, 2 or 5percent to 10, 20 or 40 percent by volume). Similarly, the duration ofthis transition zone is, in general, greater than that of the base zone,but less than that of the body zone (e.g., a duration of from 1, 2 or 5percent to 10, 20 or 40 percent that of the sum of the durations of thebase zone, the transition zone, and the body zone (e.g., less than 1, 2or 5 percent).

Immediately following the transition zone of the process (or, if notransition zone is included, immediately following the base zone of theprocess), there is a body zone, during which the remainder of thethree-dimensional object is formed. In the illustrated embodiment, thebody zone is carried out with illumination at a lower dose than the basezone (and, if present, preferably at a lower dose than that in thetransition zone), and the reciprocation steps are (optionally but insome embodiments preferably) carried out at a smaller displacement thanthat in the base zone (and, if present, optionally but preferably at alower displacement than in the transition zone). In general, a majorportion, typically greater than 60, 80, or 90 percent by volume, of thethree-dimensional object is produced during the transition zone.Similarly, the duration of this body zone is, in general, greater thanthat of the base zone and/or transition zone (e.g., a duration of atleast 60, 80, or 90 percent that of the sum of the durations of the basezone, the transition zone, and the body zone).

Note that, in this example, the multiple zones are illustrated inconnection with an oscillating mode of fabrication, but the multiplezone fabrication technique described herein may also be implemented withother modes of fabrication as illustrated further in the examples below(with the transition zone illustrated as included, but again beingoptional).

EXAMPLE 5 Fabrication with Intermittent (or “Strobe”) Illumination

The purpose of a “strobe” mode of operation is to reduce the amount oftime that the light or radiation source is on or active (e.g., to notmore than 80, 70, 60, 50, 40, or 30 percent of the total time requiredto complete the fabrication of the three-dimensional object), andincrease the intensity thereof (as compared to the intensity requiredwhen advancing is carried out at the same cumulative rate of speedwithout such reduced time of active illumination or radiation), so thatthe overall dosage of light or radiation otherwise remains substantiallythe same. This allows more time for resin to flow into the build regionwithout trying to cure it at the same time. The strobe mode techniquecan be applied to any of the existing general modes of operationdescribed herein above, including continuous, stepped, and oscillatorymodes, as discussed further below.

FIG. 11A schematically illustrates one embodiment of continuous mode. Inthe conventional continuous mode, an image is projected and the carrierstarts to move upwards. The image is changed at intervals to representthe cross section of the three-dimensional object being producedcorresponding to the height of the build platform. The speed of themotion of the build platform can vary for a number of reasons. Asillustrated, often there is a base zone where the primary goal is toadhere the object to the build platform, a body zone which has a speedwhich is suitable for the whole object being produced, and a transitionzone which is a gradual transition from the speed and/or dosages of thebase zone to the speeds and/or dosages of the body zone. Note that cureis still carried out so that a gradient of polymerization, whichprevents the formation of layer-by-layer fault lines, in thepolymerizable liquid in the build region, is preferably retained, andwith the carrier (or growing object) remaining in liquid contact withthe polymerizable liquid, as discussed above.

FIG. 11B schematically illustrates one embodiment of strobe continuousmode. In strobe continuous the light intensity is increased but theimage is projected in short flashes or intermittent segments. Theincreased intensity allows the resin to cure more quickly so that theamount of flow during cure is minimal. The time between flashes letsresin flow without being cured at the same time. This can reduceproblems caused by trying to cure moving resin, such as pitting.

In addition, the reduced duty cycle on the light source which isachieved in strobe mode can allow for use of increased intermittentpower. For example: If the intensity for the conventional continuousmode was 5 mW/cm² the intensity could be doubled to 10 mW/cm² and thetime that the image is projected could be reduced to half of the time,or the intensity could be increased 5-fold to 25 mW/cm² and the timecould be reduced to ⅕^(th) of the previous light on time.

FIG. 12A schematically illustrates one embodiment of stepped mode: Inthe conventional stepped mode an image is projected while the buildplatform is stationary (or moving slowly as compared to more rapidmovement in between illumination). When one height increment issufficiently exposed the image is turned off and the build platform ismoved upwards by some increment. This motion can be at one speed or thespeed can vary such as by accelerating from a slow speed when thethickness of uncured resin is thin to faster as the thickness of theuncured resin is thicker. Once the build platform is in the new positionthe image of the next cross section is projected to sufficiently exposethe next height increment.

FIG. 12B schematically illustrates one embodiment of strobe steppedmode: In the strobe stepped mode the light intensity is increased andthe amount of time that the image is projected is reduced. This allowsmore time for resin flow so the overall speed of the print can bereduced or the speed of movement can be reduced. For example: If theintensity for the conventional stepped mode was 5 mW/cm² and the buildplatform moves in increments of 100 um in 1 second and the image isprojected for 1 second the intensity could be doubled to 10 mW/cm², thetime that the image is projected could be reduced to 0.5 seconds, andthe speed of movement could be reduced to 50 um/second, or the time thatthe stage is moving could be reduced to 0.5 seconds. The increasedintensity could be as much as 5 fold or more allowing the time allottedfor image projection to be reduced to ⅕^(th) or less.

FIG. 13A schematically illustrates one embodiment of oscillatory mode:In the oscillatory mode an image is again projected while the buildplatform is stationary (or moving slowly as compared to more rapidmovement in-between illuminations). When one height increment is curedthe image is turned off and the build platform is moved upwards to pulladditional resin into the build zone and then moved back down to thenext height increment above the last cured height. This motion can be atone speed or the speed can vary such as by accelerating from a slowspeed when the thickness of uncured resin is thin to faster as thethickness of the uncured resin is thicker. Once the build platform is inthe new position the image of the next cross section is projected tocure the next height increment.

FIG. 13B illustrates one embodiment of strobe oscillatory mode. In thestrobe oscillatory mode the light intensity is increased and the amountof time that the image is projected is reduced. This allows more timefor resin flow so the overall speed of the print can be reduced or thespeed of movement can be reduced. For example: If the intensity for theconventional oscillatory mode was 5 mW/cm² and the build platform movesup by 1 mm and back down to an increment of 100 um above the previousheight in 1 second and the image is projected for 1 secondm theintensity could be doubled to 10 mW/cm², the time that the image isprojected could be reduced to 0.5 seconds, and the speed of movementcould be reduced to by half or the time that the stage is moving couldbe reduced to 0.5 seconds. The increased intensity could be as much as 5fold or more allowing the time allotted for image projection to bereduced to ⅕^(th) or less. Segment “A” of FIG. 13B is discussed furtherbelow.

FIG. 14A illustrates a segment of a fabrication method operated inanother embodiment of strobe oscillatory mode. In this embodiment, theduration of the segment during which the carrier is static is shortenedto close that of the duration of the strobe illumination, so that theduration of the oscillatory segment may—if desired—be lengthened withoutchanging the cumulative rate of advance and the speed of fabrication.

FIG. 14B illustrates a segment of another embodiment of strobeoscillatory mode, similar to that of FIG. 14A, except that the carrieris now advancing during the illumination segment (relatively slowly, ascompared to the upstroke of the oscillatory segment).

EXAMPLE 6 Varying of Process Parameters During Fabrication

In the methods of Example 13-14, the operating conditions during thebody zone are shown as constant throughout that zone. However, variousparameters can be altered or modified in the course of the body zone, asdiscussed further below.

A primary reason for altering a parameter during production would bevariations in the cross section geometry of the three-dimensionalobject; that is, smaller (easier to fill), and larger (harder to fill)segments or portions of the same three-dimensional object. For easier tofill segments (e.g., 1-5 mm diameter equivalents), the speed of upwardsmovement could be quick (up to 50-1000 m/hr) and/or the pump heightcould be minimal (e.g., as little at 100 to 300 um). For larger crosssectional segments (e.g., 5-500 mm diameter equivalents) the speed ofupward movement can be slower (e.g., 1-50 mm/hr) and/or the pump heightcan be larger (e.g., 500 to 5000 um). Particular parameters will, ofcourse, vary depending on factors such as illumination intensity, theparticular polymerizable liquid (including constituents thereof such asdye and filler concentrations), the particular build surface employed,etc.

In some embodiments, the overall light dosage (determined by time andintensity) may be reduced as the “bulk” of the cross section beingilluminated increases. Said another way, small points of light may needhigher per unit dosage than larger areas of light. Without wishing to bebound to any specific theory, this may relate to the chemical kinematicsof the polymerizable liquid. This effect could cause us to increase theoverall light dosage for smaller cross sectional diameter equivalents.

In some embodiments, vary the thickness of each height increment betweensteps or pumps can be varied. This could be to increase speed withdecreased resolution requirements (that is, fabricating a portion thatrequires less precision or permits more variability, versus a portion ofthe object that requires greater precision or requires more precise ornarrow tolerances). For example, one could change from 100 um incrementsto 200 um or 400 um increments and group all the curing for theincreased thickness into one time period. This time period may beshorter, the same or longer than the combined time for the equivalentsmaller increments.

In some embodiments, the light dosage (time and/or intensity) deliveredcould be varied in particular cross sections (vertical regions of theobject) or even in different areas within the same cross section orvertical region. This could be to vary the stiffness or density ofparticular geometries. This can, for example, be achieved by changingthe dosage at different height increments, or changing the grayscalepercentage of different zones of each height increment illumination.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

That which is claimed is:
 1. A method of forming a three-dimensionalobject, comprising: providing a carrier and an optically transparentmember having a build surface, said carrier and said build surfacedefining a build region therebetween; filling said build region with apolymerizable liquid, said polymerizable liquid comprising a mixture of(i) a light polymerizable liquid first component, and (ii) a secondsolidifiable component that is different from said first component,intermittently irradiating said build region with light through saidoptically transparent member to form a solid polymer from saidpolymerizable liquid first component, continuously or intermittentlyadvancing said carrier away from said build surface to form saidthree-dimensional object from said solid polymer, wherein saidintermittently irradiating comprises alternating periods of active andinactive illumination, wherein the average duration of the periods ofactive illumination is less than the average duration of the periods ofinactive illumination, and concurrently with or following the forming ofsaid solid polymer, solidifying and/or curing said second solidifiablecomponent to form said three-dimensional object, wherein: (a) saidsolidifying and/or curing step is carried out concurrently with saidirradiating step and: (i) said solidifying and/or curing step is carriedout by precipitation; or (ii) said irradiating step generates heat fromthe polymerization of said first component in an amount sufficient tothermally solidify or polymerize said second solidifiable component;and/or (b) said solidifying and/or curing step is carried out subsequentto said irradiating step and is carried out by: (i) heating said secondsolidifiable component; (ii) irradiating said second solidifiablecomponent with light at a wavelength different from that of the light insaid irradiating step; (iii) contacting said second solidifiablecomponent to water; and/or (iv) contacting said second solidifiablecomponent to a catalyst.
 2. The method of claim 1, wherein said fillingstep further comprises vertically reciprocating said carrier withrespect to said build surface to enhance or speed the refilling of saidbuild region with said polymerizable liquid.
 3. The method of claim 1,wherein said filling, irradiating, and/or advancing steps are carriedout while also concurrently: (i) continuously maintaining a dead zone ofpolymerizable liquid in contact with said build surface, and (ii)continuously maintaining a gradient of polymerization zone between saiddead zone and said solid polymer and in contact with each thereof, saidgradient of polymerization zone comprising said polymerizable liquidfirst component in partially cured form.
 4. The method of claim 1,wherein said build surface is fixed and stationary in the lateral (X andY) dimensions.
 5. The method of claim 1, wherein said advancing iscarried out at a cumulative rate of at least 0.1, 1, 10, 100 or 1000microns per second.
 6. The method of claim 3, wherein said opticallytransparent member comprises a semipermeable member, and saidcontinuously maintaining a dead zone is carried out by feeding aninhibitor of polymerization through said optically transparent member inan amount sufficient to maintain said dead zone and said gradient ofpolymerization zone.
 7. The method of claim 1, wherein said opticallytransparent member is comprised of a semipermeable polymer.
 8. Themethod of claim 3, wherein at least one of: said gradient ofpolymerization zone and said dead zone together have a thickness of from1 to 1000 microns; and/or wherein said gradient of polymerization zoneis maintained for a time of at least 5, 10, 20, or 30 seconds, or atleast 1 or 2 minutes.
 9. The method of claim 1, further comprising thestep of heating said polymerizable liquid to reduce the viscositythereof in said build region.
 10. The method of claim 6, wherein: saidpolymerizable liquid comprises a free radical polymerizable liquid andsaid inhibitor comprises oxygen; or said polymerizable liquid comprisesan acid-catalyzed or cationically polymerizable liquid, and saidinhibitor comprises a base.
 11. The method of claim 1, wherein saidsecond solidifiable component comprises a polymerizable liquidsolubilized in or suspended in said first component.
 12. The method ofclaim 1, wherein said three-dimensional object comprises a polymerblend, interpenetrating polymer network, semi-interpenetrating polymernetwork, or sequential interpenetrating polymer network formed from saidfirst component and said second solidifiable component.
 13. The methodof claim 1, wherein said solidifying and/or curing step is carried outconcurrently with said irradiating step and: (i) said solidifying and/orcuring step is carried out by precipitation; or (ii) said irradiatingstep generates heat from the polymerization of said first component inan amount sufficient to thermally solidify or polymerize said secondsolidifiable component.
 14. The method of claim 1, wherein saidsolidifying and/or curing step is carried out subsequent to saidirradiating step and is carried out by: (i) heating said secondsolidifiable component; (ii) irradiating said second solidifiablecomponent with light at a wavelength different from that of the light insaid irradiating step; (iii) contacting said second solidifiablecomponent to water; and/or (iv) contacting said second solidifiablecomponent to a catalyst.
 15. The method of claim 1, wherein: said secondsolidifiable component comprises the precursors to a polyurethane,polyurea, or copolymer thereof, a silicone resin, an epoxy resin, acyanate ester resin, or a natural rubber; and said solidifying and/orcuring step is carried out by heating and/or microwave irradiating. 16.The method of claim 1, wherein: said solidifying and/or curing step iscarried out subsequent to said irradiating step; and said solidifyingand/or curing step is carried out under conditions in which said solidpolymer degrades and forms a constituent necessary for thepolymerization of said second solidifiable component.
 17. The method ofclaim 1, wherein: said first component comprises monomers and/orprepolymers that can be polymerized by exposure to actinic radiation orlight; and said second solidifiable component is solidifiable oncontacting to heat, water, water vapor, light at a different wavelengththan that at which said first component is polymerized, catalysts,evaporation of a solvent from the polymerizable liquid, exposure tomicrowave irradiation, and combinations thereof.